The present invention is related generally to gas turbine engines and, more particularly, to systems powered by bleed air extracted from the gas turbine engine.
Gas turbine engines operate by compressing a primary air flow stream received through an inlet, combusting an air-fuel mixture within a combustor, and directing the exhaust stream of the combustion process to perform work on a turbine before discharging the exhaust. Some gas turbine engines include auxiliary flow paths that extract a portion of the primary air flow passing through a compressor section of the gas turbine engine to form a bleed air stream. Bleed air can be used to perform work ancillary to the primary combustion process of the gas turbine engine, among other functions.
For example, in a typical environmental control system (ECS), bleed air provides the air needed to power an air cycle machine (ACM) of the ECS, remove aircraft heat loads, and provide air for other functions. In particular, air cycle machines provide a means of conditioning air provided to an aircraft passenger cabin and/or other aircraft systems. Air cycle machines operate by expanding compressed bleed air across a turbine in which bleed air imparts potential and/or kinetic energy to turbine blades to cause rotation of the turbine shaft. Because bleed air extracted from a compressor section of the gas turbine engine has elevated pressure and temperature relative to an upstream compressor stage and ambient air conditions, a heat exchanger is used to reduce the bleed air temperature prior to the air cycle machine. Typically, the waste heat is discharged to the ambient environment without preforming any work and thereby reduces an overall efficiency of the gas turbine engine.
Because increasing gas turbine engine efficiency continues to be a goal for aircraft engine manufacturers, a need exists to utilize the waste bleed air heat to perform work for auxiliary engine systems and/or other aircraft systems.